Mechanical clutches are widely used in power transmissions systems between motors or engines and transmissions or other applications. Air, land, and sea vehicles, agricultural and grounds maintenance implements, construction equipment, stationary systems, and the like, all require the use of some type of clutch to disengage the engine from the application. Certain clutches, and particularly conventional motorcycle clutches, comprise a stack of friction discs and steel plates sandwiched between a generally axially fixed clutch hub and an axially moveable pressure plate. In the engaged position the friction disks and steel plates are forced together and rotate together so that power is transmitted through the clutch. In the disengaged position the disks and plates are slightly separated and do not rotate together, so power is not transmitted through the clutch.
Prior proposals for augmenting automobile and truck clutches have included various centrifugally activated members. In general such members were complicated, included several moving parts, and were expensive to make. When they malfunctioned they were generally expensive to repair. In general, motorcycle clutches had not been augmented with centrifugally activated members.
Many motorcycle clutches are of a design wherein a diaphragm spring is used to bias a pressure plate towards an engaged configuration. In general, in such designs the pressure plate moves axially relative to the diaphragm spring between engaged and disengaged configurations. The pressure plate is held in an engaged configuration by the biasing force of the diaphragm spring. Disengagement of the clutch occurs when the pressure plate is moved axially relative to the diaphragm spring in a direction against the spring bias. Where disengagement is intended to be accomplished manually, there are practical limits as to the amount of force the diaphragm spring can apply. If it requires too much force to disengage the clutch, people will not be able to operate it. There was a long felt need in the art for manually actuated diaphragm biased clutches that could exert more force than would normally be possible in a manually actuated clutch.
Previous conventional pressure plates provided a fixed amount of pressure to the clutch disks. The fixed amount of pressure was generally determined by the thickness and other characteristics of the diaphragm spring. Previously, the amount of such pressure was limited to ensure the clutch could be manually operated, and, also to allow the clutch to slip if excessive force was sent through the driveline. An unintended consequence of so limiting the amount of pressure on the clutch was that at high speeds when significant power needed to be sent through the driveline, there was undesirable slippage.
The nature of the spring that serves to bias the pressure plate determines the “feel” or behavior of the clutch during engagement and disengagement. A diaphragm spring (sometimes described as a bellville or disk spring) resists disengaging the pressure plate until the spring substantially flattens, at which point the spring force diminishes abruptly and substantially, so that little force is required to hold the clutch in the fully disengaged configuration. Diaphragm spring biased pressure plate systems tend to go very quickly from full disengagement to full engagement with little slippage.
When a clutch is required to function between a high horsepower motor (for example, over 80 horsepower) and a transmission, the clutch controls may require some augmentation. This is because the force of the required spring bias may become so great that the clutch can not be operated manually without hydraulic or other assistance. Such augmented control systems come at substantial cost in complexity, reliability, maintenance and initial price. There was a long felt need in the art for diaphragm spring biased clutches that could function with a high horsepower engine, and still be manually operated.
There are many motorcycle clutches of the diaphragm spring type in use now that were manufactured in years past. The performance of such clutches has been less than desired by their owners. There is a recognized need in the art for kits that would allow the conversion of such existing clutches to a more satisfactory configuration without excessive complexity, expense, or special tools.
Accordingly, it is an object of the invention to provide a kit for automatically augmenting the engagement pressure on the clutch of a vehicle, particularly a motorcycle, based upon engine speed.